1. Field of the Invention
This invention relates to a housing structure for housing a plurality of electric components and more particularly to a housing structure having an improved cooling characteristic.
2. Description of the Related Art
High mounting efficiency is required for this type of housing structure. This can be realized by arranging a plurality of electric components which are to-be-received members in a two- or more-storied configuration and contributes to reduction in the area for installation. Further, in a case where the electric components are hardware units such as a central processing unit or memory unit of a computer system, the following problem may be provided. That is, this type of electric component is formed to include a plurality of PC boards (print circuit boards) and a plurality of semiconductor elements such as IC elements, LSI elements and ULSI elements are mounted on the PC board. This type of semiconductor element is required to be operated under the optimum temperature condition, and at the same time, a large amount of heat is generated because of its high mounting density. Therefore, this type of housing structure is required to have the high mounting density described before and an effective cooling characteristic.
The conventional housing structure is explained with reference to FIG. 1. As shown in FIG. 1, two electric components 102 and 104 are housed or received on the upper and lower rows in a housing structure 100, thus realizing a two-storied configuration. The electric component 102 is disposed on the lower side of the housing structure 100 and the electric component 104 is disposed on the upper side of the housing structure 100. Each of the electric components 102 and 104 has a plurality of PC boards 106. An air intake port (not shown) is formed in an area ranging from the intermediate portion to the lower portion of the housing structure 100 and an air exhaust port is formed in the upper portion thereof.
Therefore, fresh air 108 introduced from the intake port of the housing structure 100 flows into the electric component 102 disposed on the lower side from the underside surface thereof and is used as intake air (cooling air) for the electric component 102. The intake air 108 upwardly passes in the electric component 102 on the lower side. Heat is carried away from the plurality of PC boards of the lower side electric component 102 by the flow of air. The thus heated intake air 108 flows out from the upper side surface of the lower side electric component 102 and acts as exhaust air 110 from the lower side electric component 102. The exhaust air 110 acts part of intake air fed to the upper side electric component 104. That is, the exhaust air 110 flows into the upper side electric component 104. Further, fresh air 112 introduced via the intake port of the housing structure 100 also flows into the upper side electric component 104. Therefore, the exhaust air 110 exhausted from the lower side electric component 102 and the fresh air 112 introduced via the intake port are combined together in the upper side electric component 104 and act as intake air (cooling air) 114 for the upper side electric component 104. The intake air 114 upwardly passes in the upper side electric component 104. Heat is carried away from the PC boards of the upper side electric component 104 by the air flow. After this, the intake air 114 is exhausted from the upper side surface of the upper side electric component 104 and is treated as exhaust air 116 from the upper side electric component 104. Finally, the exhaust air 116 is exhausted from the exhaust port of the housing structure 100 to the exterior thereof.
However, in the conventional housing structure as shown in FIG. 1, the following problem concerning the cooling characteristic is provided. That is, since air for cooling the lower side electric component 102 is the air 108 of relatively low temperature introduced via the intake port, cooling of the lower side electric component 102 can be effectively effected. However, since air for cooling the upper side electric component 104 is the air 114 of relatively high temperature obtained by combining the air 112 of relatively low temperature introduced via the intake port and the air 110 of high temperature exhausted from the lower side electric component 102, cooling of the upper side electric component 104 cannot be effectively effected. For this reason, variations may occur in the electrical characteristics caused by the cooling characteristics of the lower side electric component 102 and the upper side electric component 104. Therefore, the variations may extends the computer system to be erroneously operated.